Broadband light source sensing system and method resistant to environmental interference

Abstract

The present invention discloses a broadband light source sensing system and method that is resistant to environmental interference. The broadband light source spectrum width and the wavelength selectivity of the fiber grating are used to select a light wave of one wavelength as a reference sensing unit and perform insensitive processing on the measured signal. The light waves of other wavelengths are then used as the signal sensing unit array minus the information carried by the reference sensing unit. Since a series of noise influencing factors such as the transmission path and the detection interferometer are completely consistent, the environmental disturbance noise sources of the reference sensing unit and the signal sensing unit are highly correlated, so that the sensing system has an outstanding common-mode noise signal elimination effect. The present invention cleverly utilizes the advantages of the broadband light source spectrum width, effectively suppresses the common-mode noise of the system, and enables the broadband light source sensing array to have a higher resolution when the environment is disturbed.

Description

Technical Field

[0001] The invention belongs to the technical field of optical fiber sensing systems, and in particular relates to a broadband light source sensing system and method resistant to environmental interference. Background Art

[0002] Fiber optic sensor is a sensor that uses the wavelength selectivity of the optical fiber itself, or the change of optical physical quantity during transmission as the core measurement basis. As a new type of sensor, fiber optic sensor has many advantages such as strong electromagnetic interference resistance, high sensitivity, small size, simple structure, stable performance, etc. It can be used to measure stress, temperature, humidity and other physical quantities. Therefore, it is widely used in the fields of medicine, chemical industry, aerospace, automobile industry, resource exploration, etc., especially in the detection of weak signals. However, in the case of weak signal measurement, the fiber optic sensing system is easily affected by the instability of the wavelength of the light source, fiber transmission disturbance, external vibration, ambient temperature change and other factors. There are many kinds of noise in the final received signal. Among them, the environmental disturbance noise plays an important role in the system resolution in remote sensing. The common mode noise of this part of the fiber optic system mainly includes the phase noise caused by the external disturbance in the interferometer and the transmission path. Common mode noise will have a great impact on the measurement accuracy, so it needs to be suppressed.

[0003] Broadband light sources have the advantages of low cost, wide spectrum, and good wavelength division multiplexing compatibility. In recent years, scholars have launched a series of studies, and a series of high-resolution sensing systems driven by white light have been proposed. In practical applications, the path fiber and demodulation optical structure are subject to disturbances such as environmental vibration and temperature changes, which will introduce additional phase noise and affect the detection resolution of the sensing system. At present, the following methods for suppressing environmental noise have been proposed for sensing systems driven by broadband light sources. These include introducing a narrow linewidth laser of a reference wavelength to monitor path disturbances, and introducing a reference grating in a single grating sensing system to reduce fiber disturbance noise. However, the introduction of a narrow linewidth laser will greatly increase the cost of the system, and it is impossible to give full play to the advantages of the broadband light source system's wide spectrum and low cost. The arm length difference of the order of millimeters in the single grating system sacrifices the sensitivity of the system and limits the resolution of the sensor.

[0004] The existing broadband light source driven optical fiber sensing vibration system and method still cannot take into account the characteristics of low cost, strong resistance to environmental interference and high resolution. Summary of the invention

[0005] The present invention provides a broadband light source sensing system and method resistant to environmental interference to solve the above-mentioned technical problems, and specifically adopts the following technical solutions:

[0006] A broadband light source sensing system resistant to environmental interference, characterized by comprising:

[0007] A broadband light source module, used for emitting broadband continuous light;

[0008] Fiber Bragg grating filters are used to perform bandwidth filtering of different wavelengths of broad spectrum light;

[0009] A first erbium-doped fiber amplifier is used to amplify and adjust the optical power of the light wave after bandwidth filtering;

[0010] A second circulator, used for transmitting optical wave signals, wherein a first port of the second circulator is connected to an output end of the first erbium-doped fiber amplifier;

[0011] a long-distance transmission optical fiber connected to a second port of the second circulator;

[0012] A reference sensing unit connected to a long-distance transmission optical fiber for returning a reference light wave;

[0013] a signal sensing unit array, connected to the reference sensing unit, for returning sensing light waves;

[0014] A third coupler is connected to the third port of the second circulator and is used to split the reflected optical wave signals of different wavelengths into two paths, one optical wave signal passes through the detection path, and the other optical wave signal passes through the reference path;

[0015] The acousto-optic frequency shifter is used to shift the frequency of the optical wave signal of the reference path and remove zero-frequency noise;

[0016] A delay optical fiber is used to roughly adjust the optical path difference of the reference path to match the optical path difference between the reference path and the detection path so that it is smaller than the coherence length of the light source;

[0017] An electrically adjustable delay line for fine-tuning the optical path difference of the reference path to match the optical path difference between the reference path and the detection path to be less than the coherence length of the light source;

[0018] A fourth coupler is used to perform optical path matching heterodyne interference on the optical signals of the reference path and the detection path, and output an interference signal;

[0019] a second erbium-doped fiber amplifier, used for amplifying the optical power of the interference optical signal output by the fourth coupler;

[0020] A wavelength division multiplexing device, used for separating light waves of different wavelengths after the light waves amplified by the second erbium-doped fiber amplifier;

[0021] Two photodetectors, respectively used to detect light waves of different wavelengths separated from the wavelength division multiplexing device and perform photoelectric signal conversion;

[0022] The real-time data acquisition and processing module is used to collect and process radio frequency signals in real time, demodulate interference signals, and obtain detection results of different wavelengths.

[0023] Furthermore, the fiber Bragg grating filter includes a first circulator, a first wavelength filtering fiber Bragg grating and a second wavelength filtering fiber Bragg grating. The first circulator is used to transmit broadband light to the first wavelength filtering fiber Bragg grating and the second wavelength filtering fiber Bragg grating, and the reflected broadband light is output through the third port of the first circulator.

[0024] Furthermore, the reference sensing unit includes a first coupler, a first wavelength fiber grating pair and a reference sensing fiber, the first coupler is used to divide the transmitted light wave into two paths, one of which is input into the reference sensing fiber and then reflected by the first wavelength fiber grating first and then returned, and the other is directly reflected by the first wavelength fiber grating second and then returned;

[0025] The first wavelength fiber Bragg grating pair is used to reflect the reference light signal, and is composed of a pair of fiber Bragg gratings with the same bandwidth and center wavelength. The center wavelength of the first wavelength fiber Bragg grating pair is the same as the center wavelength of the first wavelength filtering fiber Bragg grating in the fiber Bragg grating filter, and the bandwidth is greater than the bandwidth of the fiber Bragg grating in the fiber Bragg grating filter. The reference sensing unit is insensitive to external vibrations.

[0026] The signal sensing unit array includes a second coupler, a second wavelength fiber grating pair and a signal sensing fiber. The second coupler is used to divide the transmitted light wave into two paths, one of which is input into the signal sensing fiber and then reflected by the second wavelength fiber grating 1 and then returned, and the other is directly reflected by the second wavelength fiber grating 2 and then returned;

[0027] The second wavelength fiber Bragg grating pair is used for reflecting the sensing light signal, and is composed of a pair of fiber Bragg gratings with the same bandwidth and center wavelength. The center wavelength of the second wavelength fiber Bragg grating pair is the same as the center wavelength of the second wavelength filtering fiber Bragg grating in the fiber Bragg grating filter, and the bandwidth is greater than the fiber Bragg grating bandwidth in the fiber Bragg grating filter. The signal sensing unit array is sensitive to external vibrations.

[0028] Furthermore, the broadband light source module is driven by any broadband light source such as SLD, ASE, LED light source, etc. satisfy:

[0029]

[0030] Where n is a positive integer, They represent the bandwidth of each fiber Bragg grating in the reference sensing unit and signal sensing unit array respectively.

[0031] Furthermore, the optical path length of the heterodyne interferometer is adjusted to meet the optical path difference between the detection path and the reference path. :

[0032]

[0033] in, is the central wavelength of the corresponding fiber Bragg grating, is the bandwidth of any fiber Bragg grating in the fiber Bragg grating filter, reference sensing unit and signal sensing unit array.

[0034] Furthermore, the fiber grating may be any one or more combinations of a phase-shifted fiber grating, a uniform fiber Bragg grating, and an apodized fiber grating.

[0035] Further, the reference sensing unit, the third coupler, the acousto-optic frequency shifter, the delay optical fiber, the electrically adjustable delay line and the fourth coupler constitute a reference sensing optical path matching interferometer;

[0036] The signal sensing unit, the third coupler, the acousto-optic frequency shifter, the delay optical fiber, the electrically adjustable delay line and the fourth coupler form a signal sensing optical path matching interferometer.

[0037] Furthermore, the optical path matching interferometer adopts a Michelson type structure or a Mach–Zehnder type structure and adopts a heterodyne interference method. By adjusting the optical path compensation fiber length in the reference path, the optical path of the light wave in the reference path and the detection path is made nearly consistent, thereby realizing wide-spectrum light wave interference.

[0038] A broadband light source sensing method resistant to environmental interference is applied to the aforementioned broadband light source sensing system resistant to environmental interference, and the broadband light source sensing method resistant to environmental interference comprises:

[0039] The broadband light source module emits broadband light, which enters the first port of the first circulator, is transmitted from the second port of the first circulator to the first wavelength filtering fiber grating and the second wavelength filtering fiber grating, and the light waves after different wavelength filtering are reflected back to the second port of the first circulator and output at the third port. The broadband light is subjected to bandwidth filtering of light waves of different wavelengths after passing through the fiber grating filter;

[0040] The filtered wide-spectrum light is amplified and adjusted in power by the first erbium-doped fiber amplifier, and then inputted from the first port of the second circulator, outputted from the second port to the long-distance transmission optical fiber, and then returned through the reference sensing unit a reference sensing light wave without vibration information. The light wave is divided into two light waves with equal optical power after passing through the first coupler, one light wave is reflected by the first wavelength fiber grating 1 after passing through the reference sensing optical fiber, and the other light wave is directly reflected by the first wavelength fiber grating 2. The light wave not reflected by the first wavelength fiber grating pair is then transmitted to the signal sensing unit array to return a signal sensing light wave containing vibration information. The light wave is divided into two light waves with equal optical power after passing through the second coupler, one light wave is reflected by the second wavelength fiber grating 1 after passing through the signal sensing optical fiber, and the other light wave is directly reflected by the second wavelength fiber grating 2.

[0041] The light waves reflected by the reference sensing unit and the signal sensing unit enter the second port of the second circulator after passing through the long-distance transmission optical fiber again, and are output from the third port and divided into two paths after passing through the third coupler, one light wave signal passing through the detection path, and the other light wave signal passing through the reference path; wherein, the light waves reflected by the first wavelength fiber grating 1 after passing through the reference sensing optical fiber and reflected by the second wavelength fiber grating 1 after passing through the signal sensing optical fiber pass through the reference path and are directly transmitted to the fourth coupler;

[0042] Among them, the light waves directly reflected by the first wavelength fiber grating 2 and the second wavelength fiber grating 2 pass through the detection path, first pass through the acousto-optic frequency shifter to perform frequency shifting to remove zero-frequency noise, then use the delay fiber to perform a large-scale rough adjustment of the optical path, use the electrically adjustable delay line to perform a small-scale fine adjustment of the optical path, and then transmit to the fourth coupler;

[0043] After optical path matching, when the optical path difference between the detection path and the reference path is less than the coherence length of the light wave, the two light waves undergo heterodyne interference in the fourth coupler, and the interference light is transmitted to the second erbium-doped fiber amplifier for optical power amplification and adjustment. Then, the light waves of different wavelengths are separated through the wavelength division multiplexing device, and the light waves of different wavelengths enter different photoelectric detectors for photoelectric conversion. Finally, the sensing information of the first wavelength, i.e., the reference sensing unit, and the sensing information of the second wavelength, i.e., the signal sensing unit array, enter the real-time data acquisition and processing module at the same time, and the detection results of heterodyne interference signals of different wavelengths are acquired and processed, and the information to be measured of the signal sensing unit array after eliminating the common mode noise is obtained by mixing and filtering the two.

[0044] The benefit of the present invention lies in the provided broadband light source sensing system and method that is resistant to environmental interference, which adopts a broadband light source capable of emitting broadband continuous light, fully utilizing the spectral width of the broadband light source and the wavelength selectivity of the fiber grating to simplify the optical path structure, cover a wider band, have a low cost, and are compatible with wavelength division multiplexing systems.

[0045] The benefit of the present invention lies in the provided broadband light source sensing system and method that is resistant to environmental interference, which performs mixing and filtering on the heterodyne interference signals of different wavelengths, thereby suppressing the environmental disturbance noise in the optical fiber sensing system, including a series of phase noises caused by interference with the optical fiber demodulation structure and transmission path.

[0046] The benefit of the present invention lies in that the broadband light source sensing system and method provided are resistant to environmental interference and have good noise suppression effect and high resolution during long-distance optical fiber transmission. To a certain extent, they can eliminate the influence of external vibration interference and the like during long-distance optical fiber transmission, thereby improving the signal-to-noise ratio.

[0047] The benefit of the present invention lies in the provided broadband light source sensing system and method that is resistant to environmental interference. The broadband light source spectrum width and the wavelength selectivity of the fiber grating are used to select a light wave of one wavelength as a reference sensing unit and perform insensitive processing on the measured signal. The light waves of other wavelengths are then used as the signal sensing unit array minus the information carried by the reference sensing unit. Since a series of noise influencing factors such as the transmission path and the detection interferometer are completely consistent, the environmental disturbance noise sources of the reference sensing unit and the signal sensing unit are highly correlated, so that the sensing system has an outstanding common-mode noise signal elimination effect. The present invention cleverly utilizes the advantages of the broadband light source spectrum width, effectively suppresses the common-mode noise of the system, and enables the broadband light source sensing array to have a higher resolution when the environment is disturbed. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0049] Figure 1 is a schematic diagram of a broadband light source sensing system resistant to environmental interference according to the present invention;

[0050] Figure 2 This is a time domain comparison diagram of the output signal before and after reducing the path noise of the present invention;

[0051] Figure 3 This is a comparison diagram of the output signal spectrum before and after reducing the path noise of the present invention;

[0052] Broadband light source module 1, fiber grating filter 2, first circulator 201, first wavelength filtering fiber grating 202, second wavelength filtering fiber grating 203, first erbium-doped fiber amplifier 3, second circulator 4, long-distance transmission fiber 5, reference sensing unit 6, first coupler 601, first wavelength fiber grating pair 602, 603, reference sensing fiber 604, signal sensing unit array 7, second coupler 701, second wavelength fiber grating pair 702, 703, signal sensing fiber 704, third coupler 8, acousto-optic frequency shifter 9, delay fiber 10, electrically adjustable delay line 11, fourth coupler 12, second erbium-doped fiber amplifier 13, wavelength division multiplexing device 14, two photodetectors 15, real-time data acquisition and processing module 16. DETAILED DESCRIPTION

[0053] The embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present application, and should not be construed as limiting the present application.

[0054] like Figure 1 The present invention shows a broadband light source sensing system that is resistant to environmental interference, including a broadband light source module 1, a fiber grating filter 2, a first erbium-doped fiber amplifier 3, a second circulator 4, a long-distance transmission fiber 5, a reference sensing unit 6, a signal sensing unit array 7, a third coupler 8, an acousto-optic frequency shifter 9, a delay fiber 10, an electrically adjustable delay line 11, a fourth coupler 12, a second erbium-doped fiber amplifier 13, a wavelength division multiplexing device 14, a photodetector 15, and a real-time data acquisition and processing module 16.

[0055] The broadband light source module 1 is used to emit broadband continuous light;

[0056] The fiber grating filter 2 is used to perform bandwidth filtering of different wavelengths of light waves on the broadband light. Specifically, the fiber grating filter 2 includes a first circulator 201, a first wavelength filtering fiber grating 202, and a second wavelength filtering fiber grating 203. The first ring 201 is used to transmit the broadband light to the first wavelength filtering fiber grating 202 and the second wavelength filtering fiber grating 203; the reflected broadband light is output through the third port of the first circulator 201.

[0057] The first erbium-doped fiber amplifier 3 is used to amplify and adjust the optical power of the light wave after bandwidth filtering.

[0058] The second circulator 4 is used to transmit optical wave signals, and a first port of the second circulator 4 is connected to an output end of the first erbium-doped fiber amplifier 3 .

[0059] The long-distance transmission optical fiber 5 is connected to the second port of the second circulator 4, and is used to place the reference sensing unit 6 and the signal sensing unit 7 in a different location for sensing detection. The second port of the second circulator 4 is connected to the long-distance transmission optical fiber 5, and is used to transmit the optical signal received from the first port to the long-distance transmission optical fiber 5 and the device behind it.

[0060] The reference sensing unit 6 is connected to the long-distance transmission optical fiber 5 for returning the reference light wave. The signal sensing unit array 7 is connected to the reference sensing unit 6 for returning the sensing light wave. Specifically, the reference sensing unit 6 includes a first coupler 601, a first wavelength fiber grating pair 602, 603 and a reference sensing optical fiber 604. The first coupler 601 is used to divide the transmitted light wave into two paths, one of which is input into the reference sensing optical fiber 604, and then reflected by the first wavelength fiber grating 1 603 and returned, and the other is directly reflected by the first wavelength fiber grating 2 602 and returned. The first wavelength fiber grating pair 602, 603 is used to reflect the reference light signal, which is composed of a pair of fiber gratings with the same bandwidth and center wavelength. The center wavelength of the first wavelength fiber grating pair 602, 603 is the same as the center wavelength of the first wavelength filtering fiber grating 202 in the fiber grating filter 2, and the bandwidth is greater than the bandwidth of the fiber grating in the fiber grating filter 2. The reference sensing unit 6 is insensitive to external vibrations after special design. The signal sensing unit array 7 includes a second coupler 701, a second wavelength fiber grating pair 702, 703 and a signal sensing fiber 704. The second coupler 701 is used to divide the transmitted light wave into two paths, one of which is input into the signal sensing fiber, and then reflected by the second wavelength fiber grating 1 703 and returned, and the other is directly reflected by the second wavelength fiber grating 2 702 and returned; the second wavelength fiber grating pair 702, 703 is used to reflect the sensing light signal, which is composed of a pair of fiber gratings with the same bandwidth and center wavelength; the center wavelength of the second wavelength fiber grating pair 702, 703 is the same as the center wavelength of the second wavelength filtering fiber grating 203 in the fiber grating filter 2, and the bandwidth is greater than the fiber grating bandwidth in the fiber grating filter 2. The signal sensing unit array 7 is sensitive to external vibrations.

[0061] Specifically, the fiber grating filter 2 includes a plurality of fiber gratings with different central wavelengths and the same bandwidth located on the same optical fiber. The optical fiber of the reference sensing unit 6 is provided with a 50:50 fiber coupler 601, a section of reference sensing fiber 604, and two fiber gratings 602, 603 with the same central wavelength as the first wavelength filtering fiber grating 202 in the fiber grating filter 2. The optical fiber of the signal sensing unit array 7 is provided with a plurality of groups of fiber gratings 702, 703 with the same central wavelength as the second wavelength filtering fiber grating 203 in the fiber grating filter 2. Except for the central wavelength, the fiber gratings in the reference sensing unit 6 and the signal sensing unit array 7 are consistent in other parameters such as bandwidth and reflectivity.

[0062] The third coupler 8 is connected to the third port of the second circulator 4, and is used to divide the reflected light wave signals of different wavelengths into two paths, one light wave signal passes through the detection path, and the other light wave signal passes through the reference path.

[0063] The acousto-optic frequency shifter 9 is used to shift the frequency of the optical wave signal of the reference path to remove zero-frequency noise. The delay fiber 10 is used to roughly adjust the optical path difference of the reference path of the detection interferometer in a large amplitude to match the optical path difference between the reference path and the detection path so that it is less than the coherence length of the light source. The electrically adjustable delay line 11 is used to finely adjust the optical path difference of the reference path of the detection interferometer in a small amplitude to match the optical path difference between the reference path and the detection path so that it is less than the coherence length of the light source. The fourth coupler 12 is used to perform optical path matching heterodyne interference on the optical signals of the reference path and the detection path, and output the interference signal. The second erbium-doped fiber amplifier 13 is used to amplify the optical power of the interference optical signal output by the fourth coupler 12. The wavelength division multiplexing device 14 is used to separate the light waves of different wavelengths after the light waves amplified by the second erbium-doped fiber amplifier 13, and transmit them to different photodetectors 15. The photodetector 15 is used to detect the interference light beat frequency signals of different wavelengths, namely the reference sensing unit 7 and the signal sensing array 7, and perform photoelectric signal conversion. The real-time data acquisition and processing module 16 is used to acquire and process radio frequency signals in real time, demodulate interference signals, and obtain detection results of different wavelengths, namely, reference sensing units and signal sensing arrays.

[0064] In the embodiment of the present application, the broadband light source module 1 is any one of SLD, ASE, and LED broadband light sources, and the bandwidth of the broadband light is satisfy:

[0065]

[0066] Where n is a positive integer, They represent the bandwidth of each fiber Bragg grating in the reference sensing unit 6 and the signal sensing unit array 7 respectively.

[0067] By adjusting the length to match the optical path of the heterodyne interferometer, the optical path difference between the detection path and the reference path is satisfied. :

[0068]

[0069] in, is the central wavelength of the corresponding fiber Bragg grating, It is the bandwidth of any fiber Bragg grating in the fiber Bragg grating filter 2 , the reference sensing unit 6 and the signal sensing unit array 7 .

[0070] The fiber grating of the present application may be any one or more combinations of a phase-shifted fiber grating, a uniform fiber Bragg grating, and an apodized fiber grating.

[0071] The present application also discloses a broadband light source sensing method resistant to environmental interference, which is applied to the aforementioned broadband light source sensing system resistant to environmental interference. The broadband light source sensing method resistant to environmental interference includes:

[0072] The broadband light source module 1 emits broadband light, which enters the first port of the first circulator 201, and is transmitted from the second port of the first circulator 201 to the first wavelength filtering fiber grating 202 and the second wavelength filtering fiber grating 203. The light waves after filtering at different wavelengths are reflected back to the second port of the first circulator 201 and output at the third port. The broadband light is bandwidth filtered at different wavelengths after passing through the fiber grating filter 2.

[0073] The filtered broad-spectrum light is amplified and adjusted in power by the first erbium-doped fiber amplifier 3, and then inputted from the first port of the second circulator 401, outputted from the second port to the long-distance transmission optical fiber 5, and then returned to the reference sensing light wave without vibration information through the reference sensing unit 6. The light wave is divided into two light waves with equal optical power after passing through the first coupler 601. One light wave is reflected by the first wavelength fiber grating 1 603 after passing through the reference sensing optical fiber 604, and the other light wave is directly reflected by the first wavelength fiber grating 2 602. The light wave not reflected by the first wavelength fiber grating 2 602, 603 is then transmitted to the signal sensing unit array 7 to return the signal sensing light wave containing vibration information. The light wave is divided into two light waves with equal optical power after passing through the second coupler 701. One light wave is reflected by the second wavelength fiber grating 1 703 after passing through the signal sensing optical fiber 704, and the other light wave is directly reflected by the second wavelength fiber grating 2 702.

[0074] The light waves reflected by the reference sensing unit 6 and the signal sensing unit 7 enter the second port of the second circulator 4 after passing through the long-distance transmission optical fiber 5 again, and are output from the third port and divided into two paths after passing through the third coupler 8, one light wave signal passes through the detection path, and the other light wave signal passes through the reference path.

[0075] The light waves reflected by the first wavelength fiber grating 1 603 after passing through the reference sensing fiber 604 and reflected by the second wavelength fiber grating 1 703 after passing through the signal sensing fiber 704 are directly transmitted to the fourth coupler 12 via the reference path.

[0076] Among them, the light waves directly reflected by the first wavelength fiber grating 2 602 and the second wavelength fiber grating 2 702 pass through the detection path, first pass through the acousto-optic frequency shifter to perform frequency shifting to remove zero-frequency noise, then use the delay fiber 10 to perform a large-scale rough adjustment of the optical path, and use the electrically adjustable delay line 11 to perform a small-scale fine adjustment of the optical path, and then transmit to the fourth coupler 12.

[0077] After optical path matching, when the optical path difference of the light waves in the detection path and the reference path is less than the coherence length of the light waves, the two light waves undergo heterodyne interference in the fourth coupler 12, and the interference light is transmitted to the second erbium-doped fiber amplifier 13 for optical power amplification and adjustment, and then passes through the wavelength division multiplexing device 14 to separate light waves of different wavelengths, and the light waves of different wavelengths enter different photoelectric detectors 15 for photoelectric conversion, and finally the sensing information of the first wavelength, i.e., the reference sensing unit 6, and the sensing information of the second wavelength, i.e., the signal sensing unit array 7, enter the real-time data acquisition and processing module 13 at the same time, and the detection results of heterodyne interference signals of different wavelengths are acquired and processed, and the information to be measured of the signal sensing unit array after eliminating the common mode noise is obtained by directly subtracting or filtering the two.

[0078] The process and principle of the system in this embodiment using a broadband light source sensing method that is resistant to environmental interference are as follows:

[0079] The reference sensing unit 6, the third coupler 8, the acousto-optic frequency shifter 9, the delay fiber 10, the electrically adjustable delay line 11 and the fourth coupler 12 constitute a reference optical path matching interferometer. The signal sensing unit 7, the third coupler 8, the acousto-optic frequency shifter 9, the delay fiber 10, the electrically adjustable delay line 11 and the fourth coupler 12 constitute a signal optical path matching interferometer. In this embodiment, the reference optical path matching interferometer and the signal optical path matching interferometer are pre-designed, and the interferometer uses a Michelson type structure or a Mach–Zehnder type structure, and adopts heterodyne interferometry. By adjusting the optical path compensation fiber length in the reference path, the optical path of the light wave in the reference path and the detection path is made close to the same, thereby realizing wide-spectrum light wave interference.

[0080] After the wide-spectrum light passes through the fiber grating filter 2, the bandwidth becomes narrower. When the light wave passes through the reference sensing unit, the light signal first passes through the first coupler 701 and is divided into two paths. One light signal is input into the reference sensing fiber 604 as the reference light, and then is reflected by the first wavelength fiber grating 1 603 and returned. The other light wave is directly reflected by the first wavelength fiber grating 2 602 and returned. After passing through the optical path matching interferometer, the two beams of light interfere with each other, and the interference light signal can be expressed as . Where A is the amplitude corresponding to the transmitted optical signal, is the visible light coefficient, is the frequency shift of the acousto-optic frequency shifter 9, t represents time, Phase noise introduced by environmental interference in the demodulated signal for the reference unit. , n is the refractive index of the optical fiber, is the interferometer arm length difference, is the central wavelength of the reference sensor unit, and are the changes in fiber length and refractive index, respectively.

[0081] When the light wave passes through the signal sensing unit, the light signal first passes through the first coupler 601 and is divided into two paths. One light signal is used as the reference light input into the signal sensing fiber 704, and then is reflected by the second wavelength fiber grating 1 703 and returned. The other light wave is directly reflected by the second wavelength fiber grating 2 702 and returned. After passing through the optical path matching interferometer, the two beams of light interfere with each other, and the interference light signal can be expressed as .in Phase noise introduced by environmental interference in the demodulated signal of the sensing unit. , is the central wavelength of the signal sensing unit. Since the optical path matching interferometer and the transmission path are consistent, when the lengths of the reference sensing fiber 604 and the signal sensing fiber 704 are equal, , and the wavelength proportional factor is close to 1, which has little effect on the environmental interference suppression effect. Therefore, the expression of the demodulated signal of the first wavelength is subtracted from the expression of the demodulated signal of the second wavelength: .

[0082] In this embodiment, artificial disturbance is applied to the delay optical fiber 10. The time domain comparison diagram of the output signal before and after the system reduces the disturbance noise of the common optical path is as follows: Figure 2 As shown, it can be seen from the experimental results that the present invention can well reduce the common optical path noise of the system and effectively suppress phase fluctuations, which further illustrates the feasibility of the system and method of the present invention.

[0083] The comparison of the output signal spectrum before and after the common mode noise reduction of the system in this embodiment is shown in the figure below. Figure 3 As shown, it can be seen from the experimental results that the noise reduction effect at kHz can reach 22dB, which further illustrates the feasibility of the system and method of the present invention.

[0084] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the above embodiments do not limit the present invention in any form, and any technical solution obtained by equivalent replacement or equivalent transformation falls within the protection scope of the present invention.

Claims

1. A broadband light source sensing system resistant to environmental interference, characterized in that: include: A broadband light source module (1) is used to emit broadband continuous light; A fiber grating filter (2) is used for bandwidth filtering of light waves of different wavelengths on the broadband light; A first erbium-doped fiber amplifier (3) is used to amplify and adjust the optical power of the light wave after bandwidth filtering; A second circulator (4) is used to transmit optical wave signals, and a first port of the second circulator (4) is connected to an output end of the first erbium-doped optical fiber amplifier (3); A long-distance transmission optical fiber (5) connected to the second port of the second circulator (4); A reference sensing unit (6), connected to the long-distance transmission optical fiber (5), for returning a reference light wave; A signal sensing unit array (7) connected to the reference sensing unit (6) for returning sensing light waves; A third coupler (8) connected to the third port of the second circulator (4) and used to split the reflected optical wave signals of different wavelengths into two paths, one optical wave signal passing through a detection path and the other optical wave signal passing through a reference path; an acousto-optic frequency shifter (9), used to shift the frequency of the optical wave signal of the reference path to remove zero-frequency noise; A delay optical fiber (10) is used to roughly adjust the optical path difference of the reference path to match the optical path difference between the reference path and the detection path so that it is smaller than the coherence length of the light source; An electrically adjustable delay line (11) is used to finely adjust the optical path difference of the reference path to match the optical path difference between the reference path and the detection path so that it is smaller than the coherence length of the light source; A fourth coupler (12) is used to perform optical path matching heterodyne interference on the reference path optical signals and the detection path optical signals, and output an interference signal; A second erbium-doped fiber amplifier (13) for amplifying the optical power of the interference optical signal output by the fourth coupler (12); A wavelength division multiplexing device (14) is used to separate light waves of different wavelengths from the light waves amplified by the second erbium-doped optical fiber amplifier (13); Two photoelectric detectors (15), respectively used to detect light waves of different wavelengths separated from the wavelength division multiplexing device (14) and perform photoelectric signal conversion; The real-time data acquisition and processing module (16) is used to acquire and process radio frequency signals in real time, demodulate interference signals, and obtain detection results of different wavelengths.

2. The broadband light source sensing system resistant to environmental interference according to claim 1, characterized in that: The fiber grating filter (2) comprises a first circulator (201), a first wavelength filtering fiber grating (202) and a second wavelength filtering fiber grating (203); the first circulator (201) is used to transmit broadband light to the first wavelength filtering fiber grating (202) and the second wavelength filtering fiber grating (203); and the reflected broadband light is output through the third port of the first circulator (201).

3. The broadband light source sensing system resistant to environmental interference according to claim 2, characterized in that: The reference sensing unit (6) comprises a first coupler (601), a first wavelength fiber grating pair (602, 603) and a reference sensing optical fiber (604), wherein the first coupler (601) is used to evenly divide the transmitted light wave into two paths, wherein one light wave is input into the reference sensing optical fiber (604), then reflected by the first wavelength fiber grating 1 (603) and then returned, and the other light wave is directly reflected by the first wavelength fiber grating 2 (602) and then returned; The first wavelength fiber grating pair (602, 603) is used to reflect a reference light signal, and is composed of a pair of fiber gratings with the same bandwidth and center wavelength. The center wavelength of the first wavelength fiber grating pair (602, 603) is the same as the center wavelength of the first wavelength filtering fiber grating (202) in the fiber grating filter (2), and the bandwidth is greater than the bandwidth of the fiber grating in the fiber grating filter (2). The reference sensing unit (6) is insensitive to external vibrations. The signal sensing unit array (7) comprises a second coupler (701), a second wavelength fiber grating pair (702, 703) and a signal sensing optical fiber (704), wherein the second coupler (701) is used to evenly divide the transmitted light wave into two paths, wherein one light wave is input into the signal sensing optical fiber, then reflected by the second wavelength fiber grating 1 (703) and then returned, and the other light wave is directly reflected by the second wavelength fiber grating 2 (702) and then returned; The second wavelength fiber grating pair (702, 703) is used to reflect the sensing light signal, and is composed of a pair of fiber gratings with the same bandwidth and center wavelength. The center wavelength of the second wavelength fiber grating pair (702, 703) is the same as the center wavelength of the second wavelength filtering fiber grating (203) in the fiber grating filter (2), and the bandwidth is greater than the fiber grating bandwidth in the fiber grating filter (2). The signal sensing unit array (7) is sensitive to external vibrations.

4. The broadband light source sensing system resistant to environmental interference according to claim 3, characterized in that: The broadband light source module (1) is any one of SLD, ASE, and LED broadband light sources. The bandwidth of the broadband light is satisfy: ； Where n is a positive integer, They respectively represent the bandwidth of each fiber Bragg grating in the reference sensing unit (6) and the signal sensing unit array (7).

5. The broadband light source sensing system resistant to environmental interference according to claim 3, characterized in that: By adjusting the length to match the optical path of the heterodyne interferometer, the optical path difference between the detection path and the reference path is satisfied. : ； in, is the central wavelength of the corresponding fiber Bragg grating, is the bandwidth of any fiber Bragg grating in the fiber Bragg grating filter (2), the reference sensing unit (6) and the signal sensing unit array (7).

6. The broadband light source sensing system resistant to environmental interference according to claim 3, characterized in that: The fiber grating may be any one or more combinations of a phase-shifted fiber grating, a uniform fiber Bragg grating, and an apodized fiber grating.

7. The broadband light source sensing system resistant to environmental interference according to claim 1, characterized in that: The reference sensing unit (6), the third coupler (8), the acousto-optic frequency shifter (9), the delay optical fiber (10), the electrically adjustable delay line (11) and the fourth coupler (12) form a reference sensing optical path matching interferometer; The signal sensing unit array (7), the third coupler (8), the acousto-optic frequency shifter (9), the delay optical fiber (10), the electrically adjustable delay line (11) and the fourth coupler (12) form a signal sensing optical path matching interferometer.

8. The broadband light source sensing system resistant to environmental interference according to claim 7, characterized in that: The optical path matching interferometer adopts a Michelson type structure or a Mach–Zehnder type structure and adopts heterodyne interference method. By adjusting the optical path compensation fiber length in the reference path, the optical path of the light wave in the reference path and the detection path is made close to the same, thereby realizing wide-spectrum light wave interference.

9. A broadband light source sensing method resistant to environmental interference, characterized in that: The broadband light source sensing system resistant to environmental interference as described in any one of claims 1 to 8, wherein the broadband light source sensing method resistant to environmental interference comprises: The broadband light source module (1) emits broadband light, which enters the first port of the first circulator (201), is transmitted from the second port of the first circulator (201) to the first wavelength filtering fiber grating (202) and the second wavelength filtering fiber grating (203), and the light waves after filtering at different wavelengths are reflected back to the second port of the first circulator (201) and output at the third port. The broadband light passes through the fiber grating filter (2) and is subjected to bandwidth filtering of light waves at different wavelengths. The filtered broad-spectrum light is amplified and adjusted in power by a first erbium-doped fiber amplifier (3), then inputted from a first port of a second circulator (4), outputted from a second port to a long-distance transmission optical fiber (5), and then returned through a reference sensing unit (6) as a reference sensing light wave without vibration information. The light wave is divided into two light waves with equal optical power after passing through a first coupler (601). One light wave is reflected by a first wavelength fiber grating (603) after passing through a reference sensing optical fiber (604), and the other light wave is directly transmitted to the reference sensing optical fiber (604). The light waves are then reflected by the first wavelength fiber grating second (602), and the light waves not reflected by the first wavelength fiber grating pair (602, 603) are then transmitted to the signal sensing unit array (7) to return the signal sensing light waves containing vibration information, and the light waves are divided into two light waves with equal optical power after passing through the second coupler (701), one light wave is reflected by the second wavelength fiber grating first (703) after passing through the signal sensing optical fiber (704), and the other light wave is directly reflected by the second wavelength fiber grating second (702); The light waves reflected by the reference sensing unit (6) and the signal sensing unit array (7) pass through the long-distance transmission optical fiber (5) again and enter the second port of the second circulator (4). They are output from the third port and are divided into two paths after passing through the third coupler (8), one light wave signal passing through the detection path and the other light wave signal passing through the reference path. Among them, the light waves reflected by the first wavelength fiber grating 1 (603) after passing through the reference sensing optical fiber (604) and the light waves reflected by the second wavelength fiber grating 1 (703) after passing through the signal sensing optical fiber (704) pass through the reference path and are directly transmitted to the fourth coupler (12). The light waves directly reflected by the first wavelength fiber grating 2 (602) and the second wavelength fiber grating 2 (702) pass through the detection path, are firstly frequency-shifted by the acousto-optic frequency shifter (9) to remove zero-frequency noise, and then the optical path is roughly adjusted by a large amplitude through the delay optical fiber (10), and the optical path is finely adjusted by a small amplitude through the electrically adjustable delay line (11), and then transmitted to the fourth coupler (12); After optical path matching, when the optical path difference of the light waves of the detection path and the reference path is less than the coherence length of the light waves, the two light waves undergo heterodyne interference in the fourth coupler (12), and the interference light is transmitted to the second erbium-doped fiber amplifier (13) for optical power amplification and adjustment. Then, the light waves of different wavelengths are separated through the wavelength division multiplexing device (14), and the light waves of different wavelengths enter different photoelectric detectors (15) for photoelectric conversion. Finally, the sensing information of the first wavelength, i.e., the reference sensing unit (6), and the sensing information of the second wavelength, i.e., the signal sensing unit array (7), simultaneously enter the real-time data acquisition and processing module (16), and the detection results of heterodyne interference signals of different wavelengths are acquired and processed. The information to be measured of the signal sensing unit array after eliminating the common mode noise is obtained by mixing and filtering the two.

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